A fuel cell system is a prospective cell because an energy amount that can be supplied per volume is likely to be nearly several times to ten times as large as that of the cell in the past and, by continuously supplying fuel to the fuel cell system, small electron equipment such as a cellular phone and a notebook PC can be continuously used for a long time.
In a fuel cell unit, an electrolyte membrane (MEA) in which a fuel electrode having a catalyst and an oxidizer electrode having a catalyst are formed on surfaces opposed to each other of the electrolyte membrane.
Fuel such as a hydrogen gas stored in a hydrogen occluded alloy tank or the like is supplied to the fuel electrode side and, on the other hand, an oxidizer such as oxygen is supplied to the oxidizer electrode side. These reactors are caused to electrochemically react with each other via the electrolyte membrane to generate electric power.
A theoretical voltage in a pair of electrolyte membranes (MEAs) is about 1.23 V. On the other hand, in a normal operation state, the electrolyte membranes are often used at about 0.7 V.
Therefore, when a higher electromotive force is required, a plurality of fuel cell units is stacked to form a fuel cell stack, whereby the respective cells are electrically arranged in series and used.
In the past, whereas the plurality of fuel cell units is stacked to form a fuel cell in a stack structure as described above, Japanese Patent No. 03559246 discloses that a fuel cell is formed as described below.
A cylindrical fuel cell unit employing a porous oxygen flow path plate in an oxidizer electrode in order to efficiently take oxygen in the air into the oxidizer electrode is used, a plurality of the fuel cell units is stacked in series, the center of the fuel cell units is tightened by a bolt to form a fuel cell in a stack structure.
However, in the technique disclosed in Japanese Patent No. 03559246, in stacking oxygen flow path plates of the respective cells as elastic porous members to form the fuel cell stack, in order to maintain electrical conductivity and seal a flow path of the fuel, it is necessary to apply a binding pressure equal to or larger than a fixed pressure by tightening the bolt. On the other hand, when the applied binding pressure is too large, the porous oxygen flow path plates are likely to be excessively compressed and obstruct the flow of oxygen. Therefore, fine adjustment by tightening of the bolt is necessary. However, since management of the fine adjustment is difficult, an increase in cost during manufacturing is caused.